<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>document-domain</title>
</head>
<body>
  <h1>document-domain b.html</h1>
  <script>
    document.domain = "example.cn";
    var name = 'b 定义的 name';
  </script>
</body>
</html>